Blue emitting organic semiconductors under high pressure:status and outlook

The microstructure of ZK40, ZK40 with 2 wt% of Nd and Gd (ZK40-2Nd and ZK40-2Gd, respectively) were investigated with optical, scanning and transmission electron microscopy, X-ray diffraction and Scanning Kelvin Probe Force Microscopy. The mechanical properties and the corrosion behaviour were correlated with the microstructure. The 2 wt% Gd addition enhanced the ductility, while the Nd addition resulted in deterioration in mechanical properties. The corrosion behaviour was also enhanced with the addition of Gd

Interactions of a zwitterionic thiophene-based conjugated polymer with surfactants

YesIn this paper we investigate the optical and structural properties of a zwitterionic poly[3-(N-(4-sulfonato-1-butyl)-N,N-diethylammonium)hexyl-2,5-thiophene] (P3SBDEAHT) conjugated polyelectrolyte (CPE) and its interaction in water with surfactants, using absorption, photoluminescence (PL), electrical conductivity, molecular dynamics simulations (MDS) and small-angle X-ray scattering (SAXS). Different surfactants were studied to evaluate the effect of the head group and chain length on the self-assembly. PL data emphasize the importance of polymer–surfactant electrostatic interactions in the formation of complexes. Nevertheless, conductivity and MDS data have shown that nonspecific interactions also play an important role. These seem to be responsible for the spatial position of the surfactant tail in the complex and, eventually, for breaking-up P3SBDEAHT aggregates. SAXS measurements on P3SBDEAHT-zwitterionic cocamidopropyl betaine (CAPB) surfactant complexes showed a specific structural organization of the system. The CAPB surfactant promotes a structural transition from pure P3SBDEAHT 3-dimensional aggregates (radius of gyration ∼85 Å) to thick cylindrical aggregates (∼20 Å) where all CAPB molecules are associated with the polymer. For molar ratios (in terms of the polymer repeat unit) >1 the SAXS interference maximum of the complexes resembles that of pure CAPB thus suggesting ongoing phase segregation in the formation of a “pure” CAPB phase.The Coimbra Chemistry Centre is supported by the Fundação para a Ciência e a Tecnologia (FCT), Portuguese Agency for Scientific Research, through the project PEst-OE/QUI/UI0313/2014. TC and BS thank FCT, which has supported this work through Postdoctoral Grants (SFRH/BPD/47181/2008 and SFRH/BPD/82396/2011, respectively). DA acknowledges CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico – Brasil, for financial support through the Grant “Bolsista do CNPq – Brasil”. The research leading to the SAXS data has received funding from the European Community's Seventh Framework Programme (FP7/2007–2013) CALIPSO under grant agreement no. 312284

Correlating charge transport to structure in deconstructed diketopyrrolopyrrole oligomers: A case study of a monomer in field-effect transistors

Copolymers based on diketopyrrolopyrrole (DPP) cores have attracted a lot of attention because of their high p-type as well as n-type carrier mobilities in organic field-effect transistors (FETs) and high power conversion efficiencies in solar cell structures. We report the structural and charge transport properties of n-dialkyl side-chain-substituted thiophene DPP end-capped with a phenyl group (Ph-TDPP-Ph) monomer in FETs which were fabricated by vacuum deposition and solvent coating. Grazing-incidence X-ray diffraction (GIXRD) from bottom-gate, bottom-contact FET architectures was measured with and without biasing. Ph-TDPP-Ph reveals a polymorphic structure with pi-conjugated stacking direction oriented in-plane. The unit cell comprises either one monomer with a = 20.89 angstrom, b = 13.02 angstrom, c = 5.85 angstrom, alpha = 101.4 degrees, beta = 90.6 degrees, and gamma = 94.7 degrees for one phase (TR1) or two monomers with a = 24.92 angstrom, b = 25.59 angstrom, c = 5.42 angstrom, alpha = 80.3 degrees, beta = 83.5 degrees, and gamma = 111.8 degrees for the second phase (TR2). The TR2 phase thus signals a shift from a coplanar to herringbone orientation of the molecules. The device performance is sensitive to the ratio of the two triclinic phases found in the film. Some of the best FET performances with p-type carrier mobilities of 0.1 cm(2)/V s and an on/off ratio of 10(6)are for films that comprise mainly the TR1 phase. GIXRD from in operando FETs demonstrates the crystalline stability of Ph-TDPP-Ph

Poly(Pyridinium Salt)s Containing 2,7-Diamino-9,9\u27-Dioctylfluorene Moieties with Various Organic Counterions Exhibiting Both Lyotropic Liquid-Crystalline and Light-Emitting Properties

A series of poly(pyridinium salt)s-fluorene main-chain ionic polymers with various organic counterions were synthesized by using ring-transmutation polymerization and metathesis reactions. Their chemical structures were characterized by Fourier Transform Infrared (FTIR), proton (1H), and fluorine 19 (19F) nuclear magnetic resonance (NMR) spectrometers. These polymers showed a number-average molecular weight (Mns) between 96.5 and 107.8 kg/mol and polydispersity index (PDI) in the range of 1.12-1.88. They exhibited fully-grown lyotropic phases in polar protic and aprotic solvents at different critical concentrations. Small-angle X-ray scattering for one polymer example indicates lyotropic structure formation for 60-80% solvent fraction. A lyotropic smectic phase contains 10 nm polymer platelets connected by tie molecules. The structure also incorporates a square packing motif within platelets. Thermal properties of polymers were affected by the size of counterions as determined by differential scanning calorimetry and thermogravimetric analysis measurements. Their ultraviolet-visible (UV-Vis) absorption spectra in different organic solvents were essentially identical, indicating that the closely spaced π-π* transitions occurred in their conjugated polymer structures. In contrast, the emission spectra of polymers exhibited a positive solvatochromism on changing the polarity of solvents. They emitted green lights in both polar and nonpolar organic solvents and showed blue light in the film-states, but their λem peaks were dependent on the size of the counterions. They formed aggregates in polar aprotic and protic solvents with the addition of water (v/v, 0-90%), and their λem peaks were blue shifted

Self-organized supramolecules of π-conjugated rodlike polymers

This thesis concerns fundamental self-organized aspects in π-conjugated polymers. Self-organization is the central issue in nanotechnology of soft condensed matter. The thesis focuses on the design and control of supramolecular hairy-rodlike molecules which are characterized by a thermotropic and preferentially aligned nanoscale structure. The major emphasis is on polypyridine, polyaniline, and polyfluorene. Because of their rodlike chain the formation of supramolecules is nontrivial. The understanding of the structure-property relations of this class of materials is vital in the development of organic high-performance opto-electronic devices. Throughout this work, synchrotron radiation and X-ray diffraction techniques have been extensively used and combined with the photophysical methods. In the first part, the ways to form hierarchic, highly ordered, and aligned lamellar smectic supramolecules of poly(2,5-pyridinediyl) complexed with dodecylbenzenesulfonic, methanesulfonic or camphorsulfonic acid and pentyl- or hexylresorcinol, octyl gallate, or octyl phenol have been developed and perfected. They have been characterized in the solution, in bulk and – in particular – in aligned films. Several new phases have been discovered and detailed structural description is given. When side groups are introduced microphase separated phases reveal a regular axial repeat but have different degrees of lateral packing regularity between molecules, varying from crystalline to liquid. Depending on composition they exhibit an order-order and then an order-disorder transition to isotropic phase. Liquid crystallinity allows facile overall alignment and results in the opto-electronic anisotropy as revealed by dichroism and polarized photoluminescence. In particular, it is shown that the hierarchic supramolecular structure of poly(2,5-pyridinediyl), camphorsulfonic acid and octyl phenol comprises of a higher level head-to-head structure of polymer and lower lamellae, stacked, and monomer related structure levels in normal, equatorial, and meridional directions, respectively. By choosing the exact components and tuning the composition a coherence length as high as 800 Å along the smectic axis has been achieved. By contrast to covalent side chains, the supramolecular side chains can be cleaved from the aligned materials, which render aligned pristine polymer and high photoluminescence quantum yield of pure polymer. The structure and phase equilibria have been designed between theory and experiment. The compilation of the results has been presented as a phase diagram in the melt state in the high polymer fraction limit. The study shows that the recent theoretical model highlights the most important mechanisms responsible for the observed phenomena and gives trends in which direction the developed system has to be adjusted to achieve the desired effects. In the second part, the thickness dependent triaxial texturing in poly(9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl) thin film on the rubbed polyimide has been identified, when thermotropic alignment has been applied. The polymer is 5/2 helix as proposed by Lieser and coworkers. It has three chain unit cell and the hexagonal-like cells of helical polymers are flattened in the direction of the surface normal and reveal two kinds of coexistent crystallites, a multiple orientation, where the greater proportion of the crystallites have a crystal axis a perpendicular to the substrate surface and where a smaller proportion is aligned with the crystal axis a parallel to the surface. This has been found to depend on the temperature and the film thickness. The overview shows a selection of unpublished results, reviews the trends in the supramolecular science discusses and reviews widely the characterization methods. In addition, a selection of further clarifications of the publications is reported. An unambigous experiment showing a hexagonal (cylindrical) supramolecular hairy-rodlike structure of polyaniline complexed with camphorsulfonic acid and hexylresorcinol is presented. A comb-shaped supramolecule of poly(4-vinylpyridine) complexed with methanesulfonic acid and octyl gallate is found to form a white lamellar self-organized structure. Characteristics in the fluid state are discussed.reviewe